Abdou Diallo is a PSG player. The French side bought the 23 year old from Borussia Dortmund and he signed a contract until 2024, a five-year deal.
Both clubs made the move official on Tuesday and although no figures were revealed, reports say he cost around 30 million euros.
Diallo played at Monaco for two seasons then joine Mainz 05 and finally Borussia Dortmund. He played 32 games last season and is widely considered one of the best defensive prospects around.
Dortmund sporting director Michael Zorc said: "Abdou wanted to accept the offer from his country of origin and for us the fee is very lucrative."